PSI - Issue 53

Mariana Cunha et al. / Procedia Structural Integrity 53 (2024) 386–396 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

393

8

f)

a)

Figure 5- Cross sectional view of the printed multi-layer

Figure 6 SEM- image showing lack of fusion defects formed in the shallow region of dilution zone (very close to the interface between the substrate)

The microstructure of the printed AISI P20+Ni steel, as shown in Figure 7 confirms an evolution along the build direction, i.e., needle like martensite in the bottom layer resulting from rapid cooling due to fast heat conduction through substrate, further evolving as tempered martensite in subsequent layers due to residual heat from previous layers. In the next layers, martensite upon tempering tends to precipitate the excess carbon, converting into more stable cementite (Javaheri, Pallaspuro et al. 2023), and finally appearing as ferrite dominant microstructure in the top layer attributed to the slowest cooling rate provided by the heat accumulation. A semi -quantitative chemical analysis was conducted using SEM-EDS analysis (Figure 8) to observe the variation of Cr and Mn content across the DED-printed cross section (from the dilution to the top most region) to further investigate the microstructural change along the height. Figure 8- Chemical Composition Profile for the printed multi-layer refers only to Cr and Mn wt. % since these two elements underwent the greatest change. From this analysis it evident that Cr and Mn wt. % depletes along the building direction of the final printed multi-layered bulk. This loss of alloying element may have contributed in the evolution of ferrite in the microstructure reaching to the top most region.